EP O 245 655 B1 discloses a process for thermally separating volatile and often heterogeneous organic or inorganic substances as well as the water content from contaminated soils, sands, sludges and comparable solid aggregates and residues.
In that process a thermal treatment with hot gases or hot steam is followed by a condensation of the resulting processing gases, which contain water vapor and pollutants. The liquid phase is withdrawn and the pollutants are removed from it by a wet chemical or physical processing. Residual gases may be thermally aftertreated or the residual pollutants may be removed from the residual gases by adsorption.
A disadvantage of that process resides in that the pollutants are transferred by the processing gases into the condensate and must be removed from the condensate by succeeding sewage purification processes.
DE 39 37 952 A1 discloses a process for purifying contaminated soils. The soils are treated with steam and the effluent vapor is condensed. In that process a layer of the soil is applied to a gas-permeable substrate in a pressurizable housing, which is supplied with steam at a temperature from 100.degree. to 190.degree. C. and under a pressure from 1 to 12 bars. That steam is supplied to the pressurizable housing and passed through the layer. The steam leaving the layer is withdrawn from the pressurizable housing and is condensed. The condensate is supplied to a purifier, and the solids are delivered as purified soil.
When the layer has been dewatered or reheated, wet steam which contains oxidizing substances may be passed through the layer. The oxidizing substance may primarily consist of air although oxygen-enriched air and/or H.sub.2 O.sub.2 may be used. A part of the effluent steam may be recycled to preheat the aqueous suspension of the contaminated soil before the latter is fed. Because the layer of contaminated soil is stationary relative to the substrate, the contaminated material is not moved.
EP 0 252 521 B1 discloses a process for decomposing polyhalogenated cycloalkyl compounds having 4 to 8 carbon atoms and of polyhalogenated aromatic compounds having at least 5 carbon atoms. That process comprises heating in the presence of a catalyst. In that process the volatile constituents are present in a solid substrate, which is contaminated with polyhalogenated compounds, or in a liquid substrate which is contaminated with the polyhalogenated compounds, or in a liquid substrate which is contaminated with the polyhalogenated compounds and the volatile constituents or the liquid substrate or the polyhalogenated compounds themselves may be converted to a gas by heating or combustion and the resulting gases or a gaseous substrate which is contaminated with the polyhalogenated compounds is or are heated in close contact with the catalyst and in the presence of oxygen and water.
The process is carried out in the presence of oxygen and water to ensure that the catalysts will mainly be preserved as an oxide material and that HC1 rather than chlorine will be formed as the polyhalogenated compounds are destroyed.